Characteristics and Availability of Commercially Important Woods Regis B
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Chapter 1 Characteristics and Availability of Commercially Important Woods Regis B. Miller hroughout history, the unique characteristics and Contents T comparative abundance of wood have made it a natural material for homes and other structures, furniture, tools, vehicles, and decorative objects. Today, for Timber Resources and Uses 1–2 the same reasons, wood is prized for a multitude of uses. All wood is composed of cellulose, lignin, hemicelluloses, Hardwoods and Softwoods 1–2 and minor amounts (5% to 10%) of extraneous materials Commercial Sources of Wood Products 1–2 contained in a cellular structure. Variations in the characteris- tics and volume of these components and differences in cellu- Use Classes and Trends 1–3 lar structure make woods heavy or light, stiff or flexible, and hard or soft. The properties of a single species are relatively Species Descriptions 1–3 constant within limits; therefore, selection of wood by spe- cies alone may sometimes be adequate. However, to use U.S. Wood Species 1–3 wood to its best advantage and most effectively in engineer- ing applications, specific characteristics or physical properties Hardwoods 1–3 must be considered. Softwoods 1–10 Historically, some species filled many purposes, while other less available or less desirable species served only one or two Imported Woods 1–17 needs. For example, because white oak is tough, strong, and durable, it was highly prized for shipbuilding, bridges, Hardwoods 1–17 cooperage, barn timbers, farm implements, railroad crossties, fence posts, and flooring. Woods such as black walnut and Softwoods 1–33 cherry were used primarily for furniture and cabinets. Hickory was manufactured into tough, hard, and resilient striking-tool References 1–34 handles, and black locust was prized for barn timbers. What the early builder or craftsman learned by trial and error be- came the basis for deciding which species were appropriate for a given use in terms of their characteristics. It was com- monly accepted that wood from trees grown in certain loca- tions under certain conditions was stronger, more durable, more easily worked with tools, or finer grained than wood from trees in other locations. Modern research on wood has substantiated that location and growth conditions do significantly affect wood properties. The gradual reductions in use of old-growth forests in the United States has reduced the supply of large clear logs for lumber and veneer. However, the importance of high-quality logs has diminished as new concepts of wood use have been introduced. Second-growth wood, the remaining old-growth forests, and imports continue to fill the needs for wood in the quality required. Wood is as valuable an engineering mate- rial as ever, and in many cases, technological advances have made it even more useful. 1–1 The inherent factors that keep wood in the forefront of raw or sap in the tree. Typically, hardwoods are plants with materials are many and varied, but a chief attribute is its broad leaves that, with few exceptions in the temperate re- availability in many species, sizes, shapes, and conditions to gion, lose their leaves in autumn or winter. Most imported suit almost every demand. Wood has a high ratio of strength tropical woods are hardwoods. Botanically, softwoods are to weight and a remarkable record for durability and perform- Gymnosperms or conifers; the seeds are naked (not enclosed ance as a structural material. Dry wood has good insulating in the ovary of the flower). Anatomically, softwoods are properties against heat, sound, and electricity. It tends to nonporous and do not contain vessels. Softwoods are usually absorb and dissipate vibrations under some conditions of cone-bearing plants with needle- or scale-like evergreen use, and yet it is an incomparable material for such musical leaves. Some softwoods, such as larches and baldcypress, instruments as the violin. The grain patterns and colors of lose their needles during autumn or winter. wood make it an esthetically pleasing material, and its appearance may be easily enhanced by stains, varnishes, Major resources of softwood species are spread across the lacquers, and other finishes. It is easily shaped with tools United States, except for the Great Plains where only small and fastened with adhesives, nails, screws, bolts, and dow- areas are forested. Softwood species are often loosely grouped els. Damaged wood is easily repaired, and wood structures in three general regions, as shown in Table 1–1. Hardwoods are easily remodeled or altered. In addition, wood resists also occur in all parts of the United States, although most oxidation, acid, saltwater, and other corrosive agents, has grow east of the Great Plains. Hardwood species are shown high salvage value, has good shock resistance, can be treated by region in Table 1–2. with preservatives and fire retardants, and can be combined with almost any other material for both functional and Commercial Sources esthetic uses. of Wood Products Timber Resources and Uses Softwoods are available directly from the sawmill, wholesale and retail yards, or lumber brokers. Softwood lumber and In the United States, more than 100 wood species are avail- plywood are used in construction for forms, scaffolding, able to the prospective user, but all are unlikely to be avail- framing, sheathing, flooring, moulding, paneling, cabinets, able in any one locality. About 60 native woods are of major poles and piles, and many other building components. Soft- commercial importance. Another 30 species are commonly woods may also appear in the form of shingles, sashes, imported in the form of logs, cants, lumber, and veneer for doors, and other millwork, in addition to some rough prod- industrial uses, the building trade, and crafts. ucts such as timber and round posts. A continuing program of timber inventory is in effect in the Hardwoods are used in construction for flooring, architectural United States through the cooperation of Federal and State woodwork, interior woodwork, and paneling. These items agencies, and new information on wood resources is pub- are usually available from lumberyards and building supply lished in State and Federal reports. Two of the most valuable dealers. Most hardwood lumber and dimension stock are sourcebooks are An Analysis of the Timber Situation in the remanufactured into furniture, flooring, pallets, containers, United States 1989–2040 (USDA 1990) and The 1993 RPA dunnage, and blocking. Hardwood lumber and dimension Timber Assessment Update (Haynes and others 1995). Current information on wood consumption, production, Table 1–1. Major resources of U.S. softwoods according imports, and supply and demand is published periodically to region by the Forest Products Laboratory (Howard 1997) and is available from the Superintendent of Documents, U.S. Western Northern Southern Government Printing Office, Washington, DC. Incense-cedar Northern white-cedar Atlantic white-cedar Port-Orford-cedar Balsam fir Baldcypress Hardwoods and Softwoods Douglas-fir Eastern hemlock Fraser fir White firs Fraser fir Southern Pine Trees are divided into two broad classes, usually referred to Western hemlock Jack pine Eastern redcedar as hardwoods and softwoods. These names can be confusing Western larch Red pine since some softwoods are actually harder than some hard- Lodgepole pine Eastern white pine woods, and conversely some hardwoods are softer than some Ponderosa pine Eastern redcedar softwoods. For example, softwoods such as longleaf pine and Sugar pine Eastern spruces Douglas-fir are typically harder than the hardwoods basswood and aspen. Botanically, hardwoods are Angiosperms; the Western white pine Tamarack seeds are enclosed in the ovary of the flower. Anatomically, Western redcedar hardwoods are porous; that is, they contain vessel elements. Redwood A vessel element is a wood cell with open ends; when vessel Engelmann spruce elements are set one above another, they form a continuous Sitka spruce tube (vessel), which serves as a conduit for transporting water Yellow-cedar 1–2 Table 1–2. Major resources of U.S. hardwoods according to region Species Descriptions Northern and In this chapter, each species or group of species is described Southern Appalachia Western in terms of its principal location, characteristics, and uses. More detailed information on the properties of these and Ash Ash Red alder other species is given in various tables throughout this Basswood Aspen Oregon ash handbook. Information on historical and traditional uses is American beech Basswood Aspen provided for some species. Common and botanical names Butternut Buckeye Black cottonwood follow the Checklist of United States Trees (Little 1979). Cottonwood Butternut California black oak Elm American beech Oregon white oak Hackberry Birch Bigleaf maple U.S. Wood Species Pecan hickory Black cherry Paper birch True hickory American chestnuta Tanoak Hardwoods Honeylocust Cottonwood Alder, Red Black locust Elm Magnolia Hackberry Red alder (Alnus rubra) grows along the Pacific coast be- Soft maple True hickory tween Alaska and California. It is the principal hardwood for Red oaks Honeylocust commercial manufacture of wood products in Oregon and White oaks Black locust Washington and the most abundant commercial hardwood Sassafras Hard maple species in these two states. Sweetgum Soft maple The wood of red alder varies from almost white to pale American sycamore Red oaks pinkish brown, and there is no visible boundary between Tupelo White oaks heartwood and sapwood. Red alder is moderately light in Black walnut American sycamore weight and intermediate in most strength properties but low Black willow Black walnut in shock resistance. It has relatively low shrinkage. Yellow-poplar Yellow-poplar aAmerican chestnut is no longer harvested, but chestnut The principal use of red alder is for furniture, but it is also lumber from salvaged timbers can still be found on the used for sash and door panel stock and other millwork. market. Ash (White Ash Group) Important species of the white ash group are American white stock are available directly from the manufacturer, through ash (Fraxinus americana), green ash (F.